The present invention relates generally to a volume hologram medium, and more particularly to a volume hologram medium improved in terms of aesthetics and security.
Patent Publication 1 proposes a hologram medium in which a stereoscopic image and a pupil image comprising a repetition of usually invisible fine patterns are recorded in a volume hologram to determine whether the hologram is genuine or fake through a pattern reconstructed pattern from that pupil image.
Patent Publication 2 proposes a hologram medium in which a volume hologram medium is deactivated in a fine repetitive pattern using ultraviolet radiation to record an object image in the remaining photosensitive area, so that whether the hologram is genuine or fake is judged by the deactivated pattern.
Patent Publication 1
JP-A 11-24538
Patent Publication 2
JP-A 11-277958
Both the hologram media proposed in the above patent publications 1 and 2 are satisfactory in terms of security, but they are not always satisfactory in terms of aesthetics because the fine patterns used for authentication are invisible.